Local exchanges and transit exchanges in current voice telephony networks (PSTN/ISDN=Public Switched Telephone Network/Integrated Services Digital Network) which are based upon the principle of circuit switching (TDM=Time Division Multiplex) deal with the control of links and useful channels (e.g. two-party links, tripartite links, feeding of tones).
Next generation networks (e.g. ATM=Asynchronous Transfer Mode, IP=Internet Protocol) which are designed for voice and data work according to the principle of separation in the control of links and useful channels. Thus, in next generation networks (NGN), unlike in PSTN/ISDN, different network elements are used to control links and useful channels. Here, link control is carried out by soft switches which communicate by means of a suitable media gateway control protocol with the media gateways controlling the useful channel. The soft switches in the NGN communicate with one another via a suitable signaling protocol, e.g. BICC=Bearer Independent Call Control, in a similar way to the PSTN/ISDN switching points, where e.g. signaling system No. 7 (CCS7) is used.
FIG. 1 shows the principle of current PSTN/ISDN networks, while FIG. 2 represents the principle of voice communication in next generation networks NGN.
An example of the structure of a next generation network is known from the publication WO 01/59999. WO 01/59999 discloses a next generation communication network with service generation switches which control media gateways of the next generation network by means of a control protocol, the media gateways replacing hardware of a conventional public telephone network (PSTN/ISDN). WO 01/59999 also describes a method for controlling services in such a network.
A plurality of subscriber and network services are implemented in current PSTN/ISDN networks, said services continuing to be needed by end customers and network operators, irrespective of the technical implementation. Implementation of these services affects as a rule the control of links and useful channels.
The split of functions in NGNs, i.e. separation of the control of links VStrg and the control of useful channels NStrg prevents the use of control software of current switching points in NGNs. The soft switches SoftSW which deal with link control in the NGNs, should preferably be formed by standard computers and in this way replace the highly specialized switching processors.
The problem arises here that the new development or porting of the software controlling PSTN/ISDN services for standard computers is extremely costly and very complex. Furthermore, a soft switch has to be interoperable with classic transit exchanges, that is be capable of managing the relevant classic signaling protocols and procedures, because the current PSTN/ISDN network and the next generation networks will coexist for quite a long time.
This problem arises again as a consequence of the use of next generation networks for providing classic telephony services (replication of the PSTN/ISDN). Known proposed solution to date are:                New development of the control software on commercial platforms        Specific further development of classic switching points.        